Fraction of Inspired Oxygen
Expressed as a percentage or a decimal. The air we breathe (room air) contains 21% oxygen. Room air FiO2 is expressed at 21% or 0.21. Below is a chart comparing the FiO2 of common oxygen delivery methods.
| Nasal Cannula at 2 lpm | 28% |
| Nasal Cannula at 4 lpm | 36% |
| Nasal Cannula at 6 lpm | 44% |
| Non-Rebreather at 12-15 lpm | 80-100% |
| BVM at 15 lpm | 95-100% |
The most common strategy for determining FiO2 with a vented patient is to start with 100% and titrate down from there to maintain goal SpO2 and PaO2.